In general, grease is a kind of lubricant that is supplied to form an oil film between components of a rotation part, such as a roller or a bearing, subjected to a large load. Such grease is supplied in a semi-solid state, turns into a liquid state by pressure and heat when a machine is operated, and changes into the semi-solid state again when the machine is stopped.
Therefore, if the grease is not supplied between the rotation components, burn out or seizures occur due to friction, so that a worker has to frequently check the amount of grease and replenish the grease sufficiently as necessary.
Such grease has a high viscosity, and a grease gun is used to inject a small amount of grease. However, when it is necessary to inject a large amount of grease having a high viscosity, a separate automatic grease injection pump to supply the grease to the machine.
Such an automatic grease injection pump has been developed, and an example thereof is disclosed in Korean Patent Application Publication No. 2013-129581 (hereinafter referred to as “Related art document 1”).
FIG. 1 is a mew showing a conventional automatic grease injection apparatus disclosed in Related art document 1.
As shown in FIG. 1, the conventional automatic grease injection apparatus includes: a pumping device 110 for supplying grease accommodated in a tank 112; a driving device for driving the pumping device 110; a supply pipe 120 for supplying the grease discharged from the pumping device 110; a grease distribution unit 121 provided at an end on a downstream side of the supply pipe 120; a check valve 128 installed in the supply pipe 120 to prevent the grease from flowing backward; a circulation pipe 130 in communication with the supply pipe 120 for circulating the grease to the pumping device 110; a relief valve 132 installed in the circulation pipe 130 so as to be opened and closed according to pressure in the circulation pipe 130; and a control unit 140 for controlling the driving device in each mode. In this case, the grease distribution unit 121 includes: a main function supply pipe 121a for supplying the grease to equipment; an auxiliary function supply pipe 121b for supplying the greases to a composite attachment; and a three-way pipe 126 for selectively supplying the grease to the main function supply pipe 121a and the auxiliary function supply pipe 121b. In addition, a cylinder 116 is installed at the center of the pumping device 110 in order to supply the grease from a bottom of the pumping device 110.
However, the conventional automatic grease injection apparatus disclosed in Related art document 1 injects a fixed amount of grease, so that it is suitable for dedicated equipment prepared in the stage of manufacturing, whereas when the grease is supplied to other equipment, excessively supplied grease may contaminate the equipment, and insufficiently supplied grease may cause the burn out of the equipment.
In addition, since a discharge amount of the grease cannot be controlled, the precision of the discharge amount of the grease is decreased when the automatic grease injection apparatus is used for a long period of time.
Further, when air is introduced into the grease, an air pocket is formed, so that the grease sucked through the cylinder may not be supplied in an appropriate amount.
In addition, if foreign substances are contained in the grease circulated through the circulation pipe, the contaminated grease is supplied through the cylinder.